As small consumer electronics such as mobile phones and personal digital assistants (PDAs) continue to proliferate at an unprecedented rate, the need for smaller and more reliable integrated circuit (IC) chip packaging has increased. IC chip packaging includes forming an encapsulant over the IC chips to protect the IC chips from being damaged by external factors. This encapsulant may be referred to as a “mold cap” formed over the IC chips. As the size of electronic devices decreases, there is a continuing need for thinner and thinner mold caps.
One current technique for forming mold caps over IC chips is transfer molding of encapsulant over IC chips. In transfer molding, an IC structure including IC chips affixed to a substrate is placed in a mold designed to allow encapsulation to a specified area. Mold compound is then liquefied by heat and pressure, and transferred into the mold. The mold cap solidifies around the IC chips as the mold compound is cooled. Transfer molding techniques are commonly used for encapsulating chip-size packages (CSP's). However, there are various problems commonly associated with transfer molding, particularly due to high operating temperatures and high pressures required to fill the mold. Such problems include incomplete filling of mold due to rapid curing of the mold compound, thermal stresses, displacement of bonding wires, and overpacking or resin bleed (commonly referred to as “flash”), for example.
Another current technique for forming mold caps over IC chips is compression molding using powderized mold compound. The powderized mold compound is spread out in a cavity in a mold die and an IC structure including IC chips affixed to a substrate is compressed into the powderized mold compound to form a solid mold cap around the IC chips. However, like the transfer molding techniques discussed above, compression molding using powderized mold compound suffers from various problems. Such problems include, for example, difficulties in evenly spreading a very thin layer of powderized mold compound into the mold die cavity, crumbling of the resulting mold cap, and inefficient machine tact time caused by the need to refill the mold die cavity with powder after each compression molding process.